1. Field of the Invention
The present invention relates to storage type water heaters. Particularly, the present invention relates to improved apparatus and methods for distributing water in the water storage tank of a water heater for improving thermal efficiency. More particularly, the present invention relates to improved methods and apparatus for mixing incoming cold water with heated water in the water storage tank for eliminating stratification of water according to temperature and for preventing intrusion of cold water streamers into the heated water in the upper portion of the water storage tank.
2. Description of Pertinent Art
Storage type water heaters, as contemplated herein, typically comprise a vertical, cylindrical water rank having a cold water supply tube, (commonly referred to as a xe2x80x9cdip tubexe2x80x9d), extending internally from the top of the water tank to a point near the bottom of the water rank, and having a hot water outlet near the top of the water tank, Such water heaters may employ gas heat or electrical heat for heating water. Typically, such water heaters are employed to heat cold water from a temperature of often 58xc2x0 F. or lower to temperatures in the range of about 120xc2x0 to 140xc2x0 F. The heated water is stored in the water tank for use as the demand arises.
Such water heaters as are heated by gas generally comprise a vertical, cylindrical water tank having a centrally located gas flue passing vertically through the water tank. A radial flame gas burner, located directly below the bottom of the water tank heats water in the water tank. Additional heat is transferred to water in the water tank from hot combustion gasses produced by the burner passing upward through the gas flue. Flue baffles and similar apparatus are commonly employed in the gas flue for improving heat transfer from the combustion gasses to the water in the tank. Combustion gases are exhausted from the gas flue near the top of the water heater.
Such water heaters as are heated by electricity generally comprise a vertical cylindrical water tank having one or more electrical resistance heating elements mounted at intermediate elevations in the water tank. Heat is exchanged between the heating elements and water in the water tank.
Cold water is supplied to a storage type water heater through a dip tube. As hot water is withdrawn from an outlet near the top of the tank, cold water flows down the dip tube and is deposited near the bottom of the tank. Water in the tank is heated, by either electric elements or gas burners, creating a water temperature gradient with the hottest water near the top of the tank and the coolest water at the bottom. The velocity and uneven distribution of water discharging from the dip tube often result in streamers of cold water flowing upwardly in the tank, disturbing the water temperature gradient and sometimes allowing cold water to discharge from the hot water outlet.
Methods and apparatus for improving distribution of cold water and preventing convection currents of cold water in the tank of a water heater are known in the art. In U.S. Pat. Nos. 4,949,680; 5,054,437; 5,137,053; and 6,199,515 B1, means including baffles and diffusers are provided for distributing cold water from the dip tube evenly across the bottom diameter of the tank and thereby preventing streamers of unheated water from rising within the tank.
In U.S. Pat. No. 4,949,680 the vertical dip tube, through which cold water enters the tank, is positioned at or near the central axis of the tank for exchanging heat between heated water in the tank and cold water entering through the dip tube, thus foiling thermal convection currents from rising in the tank and minimizing the mixing of hot and cold water near the hot water discharge outlet.
U.S. Pat. Nos. 4,632,065 and 5,809,941 disclose internal baffles within the water hearer tank for foiling internal thermal convection currents within the tank and minimizing mixing of hot and cold water near the hot water discharge outlet from the tank.
U.S. Pat. No. 4,197,446 discloses a water heater comprising a storage rank, a cold water inlet means comprising an external water heater connected to the water tank, a jet pump in the cold water inlet and a hot water discharge faucet. In operation, when hot water is discharged through the hot water faucet, cold water enters the tank trough the jet pump, causing water to be drawn from the tank into die external heater where the water is heated to discharge temperature. A portion of the hot water from the external heater is drawn i-nto the jet pump where the hot water mixes with the entering cold water. This water mixture is discharged into the rank where it is maintained at an intermediate temperature without further heating in the tank.
British Provisional Specification GB 648,213 discloses a water heater comprising a tank, a first tube vertically arrayed in the tank and having an open top, an external heater in communication with the external lower portion the first tube, and a second tube having a first open end in communication with the lower portion of the tank and a second open end in communication with the interior of the first tube lower portion. In operation, the external heater heats water in the lower portion of the first tube. As heated water rises in the first tube, cooler water from the lower portion of the water tank is drawn in to the lower portion of the first tube through the open second tube. Heated water from the first tube is discharged near the top of the tank.
Now, according to the present invention, I have discovered apparatus and methods for improving thermal efficiency and uniformity of hot water discharge temperature in a storage type hot water heater.
A storage type water heater comprising: a water tank having a cold water inlet and a hot water outlet, and a dip tube having a dip tube inlet connected to the cold water inlet, and having a dip tube outlet discharging into the lower portion of the water tank, the improvement of the present invention comprises:
a). a first flow regulator in the cold water inlet for regulating the flow of cold water into the water tank;
b). one or more mixing means in the dip tube for mixing incoming cold water with warm water from the water tank;
c). distributor means for distributing water discharged from the dip tube outlet evenly into the lower portion of the water tank; and
d). a second flow regulator in the hot water outlet for regulating flow of hot water from the water heater.
The apparatus of the present invention further includes baffle means in the mid portion of the water tank for preventing the upward flow of cooler water to the hot water outlet.